Here's why:

* Cellular Respiration: Mitochondria are the powerhouses of the cell. They are responsible for cellular respiration, a process that breaks down glucose (sugar) in the presence of oxygen to produce ATP (adenosine triphosphate). ATP is the primary energy currency of cells.

* Krebs Cycle and Electron Transport Chain: The key steps in cellular respiration, the Krebs cycle and the electron transport chain, occur within the mitochondria.

* Energy Production: Mitochondria use the energy stored in the chemical bonds of glucose to create ATP, which fuels various cellular activities, such as muscle contraction, protein synthesis, and active transport.